<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>03_回调ref的回调次数问题</title>
</head>

<body>
    <div id="app"></div>

    <script src="../js/react.development.js"></script>
    <script src="../js/react-dom.development.js"></script>
    <script src="../js/babel.min.js"></script>

    <script type="text/babel">
        class MyComponent extends React.Component{
            state = {
                isHot:true
            }
            // 点击按钮触发
            showInfo = ()=>{
                let {isHot} = this.state
                // 更新组件状态触发render方法
                this.setState({
                    isHot:!isHot
                })
            }
            render(){
                const {isHot} = this.state
                return (
                    <div>
                        <div>今天的天气很 {isHot ? '晴朗' : '阴沉'}</div>
                        <div>
                            <input ref={(cNode)=>{
                                // 在组件更新过程中，ref的回调会被执行两次，第一次回调参数是null，第二次是真正的DOM
                                this.input = cNode;
                                console.log('@',cNode);
                            }} placeholder="输入内容"/>
                            <button onClick={this.showInfo}>点击提示信息</button>
                        </div>
                    </div>
                )
            }
        }

        ReactDOM.render(<MyComponent/>,document.getElementById("app"))
    </script>
</body>

</html>